The present invention offers many advantages over previous port systems. DE 41 29 782 C1 describes a port system that comprises a port and a catheter. The port has a housing with an opening at the bottom to receive the active substance and an opening at the top to receive the membrane. The membrane is held in the opening by a clamping ring which exerts a pressure on the membrane so that the membrane curves outwards. The use of a clamping ring is disadvantageous because it makes it difficult to secure the membrane over the opening. For example, in an adhesive-bonded or welded connection, it is necessary for the clamping ring, which is under pressure, to be held in position against the housing until the adhesive has cured.
For the connection of the catheter, the known port has a tapering connecting piece that is in fluid connection with the central opening in the housing. The catheter is pushed onto the tapering connecting piece. The catheter is fixed to the connecting piece by means of a clamping sleeve which is screwed to the housing. A coupling of this kind for flexible lines is described in detail in DE 41 29 781 A 1. It is a disadvantage that, once the clamping sleeve has been fitted, it cannot be seen how far the catheter has been pushed onto the tapering connecting piece. Further, if not properly fitted, there is a risk the flexible catheter will come loose from the connecting piece. Still further, it is a disadvantage that the clamping sleeve is a separate component and can easily be lost.
When an active substance is injected with a needle, care must be taken to ensure that the membrane situated beneath the skin is accurately targeted. If the needle impacts the housing, instead of the membrane, there is a possibility the needle will slip off the housing and strike the catheter.